This invention relates generally to a system and method for communicating information between one or more sensors and at least one receiver or station at which a person may obtain information regarding the contents of one or more containers, and more particularly to a system which allows fire fighters, rescue workers, and other emergency personnel to identify, from a remote location, the specific hazardous substance stored in each container, thereby allowing the risk of explosion, contamination, or other uncontrolled release of hazardous substances to be quickly and safely evaluated at an accident site.
An important requirement in transporting hazardous materials such as flammable or corrosive substances, is that both the containers and the vehicles transporting them be clearly and conspicuously labelled to identify the dangerous properties of the cargo within. In the case of over-the-road transportation, the labelling allows regulatory personnel to determine whether the vehicle driver has selected an improper route (such as through a tunnel where vehicles carrying hazardous materials are not permitted) or prompts them to verify that all applicable safety procedures have been taken. In the case of accident or fire, conspicuous labelling further alerts members of the public as well as emergency personnel arriving at the scene to the elevated risk of physical injury which could result from an explosion or other uncontrolled release of the hazardous substance.
While stringent labelling requirements are obviously a critical element of a safe hazardous material transportation system, however, there are certain limitations which have heretofore remained unaddressed. Specifically, while a "flammable" label on the side of a truck alerts emergency personnel to the risk of fire or explosion, it does not reveal the specific contents of the drums or barrels being transported thereby. Further, where an emergency situation such as a fire exists, it may be inadvisable to venture close enough to the vehicle to read the labels on the drums themselves. The resulting lack of information may force emergency personnel to use procedures reserved for the highest risk situations, even where relatively stable hazardous materials are involved.
Devices for monitoring temperature, pressure or other conditions in a transport container and transmitting data corresponding to said conditions have been proposed in the past. For example, in U.S. Pat. No. 5,095,739 entitled TANK LEAK DETECTOR, which issued on Mar. 17, 1992 to Robert C. Hedtke, there is proposed a system which utilizes a pressure sensitive transmitter positioned within the tank. The transmitter uses either an absolute pressure sensor or a differential pressure sensor to detect any changes in the liquid level within the tank and transmits an output signal corresponding to the change via an output cable. While the '739 system allows a condition in a transportable container to be monitored from outside the container, it relies on an output cable between the sensor location and the monitoring station and is thus limited in range to the transport carrier itself. Further, the '739 system provides no means for determining the contents of the one or more tanks from a safe distance during a fire or other emergency.
In U.S. Pat. No. 4,882,564 entitled REMOTE TEMPERATURE MONITORING SYSTEM, which issued on Nov. 21, 1989 to Monroe et al, there is disclosed a remote temperature monitoring system for a refrigerated trailer in which a temperature sensor such as a thermistor and transmitter unit are positioned in a transport container and a display receiver unit is provided at a remote location in the cab compartment. The temperature sensor generates an output voltage dependent upon the temperature sensed and a frequency shift keyed output signal is transmitted to a display unit via an output cable. The output signal is received by the display unit, which displays the sensed temperature, and is compared to an alarm limit corresponding to an upper temperature threshold for possible triggering of an alarm in the display unit. Like the '739 system, the range of the '564 system is limited because it relies on an output cable between the sensor in the trailer and the monitoring station. Also, the '564 system is not adapted to permit the contents of one or more trailers to be determined from a remote location.
In U.S. Pat. No. 3,764,984, entitled INFORMATION CODING SYSTEM and issued on Oct. 9, 1973 to James S. McCartney, there is disclosed an information coding system in which a plurality of remote sensing units are monitored by a radio link with a central monitoring station. Each sensing unit is adapted to monitor a condition such as temperature, power loss, or unauthorized entry and to generate an alarm signal when a certain condition occurs. Alarms of each particular type of sensing unit are similarly coded and each sensing unit is adapted to generate a series of marker pulses which uniquely identify the location of that particular unit when it is activated.